Method of connecting a plate-shaped absorber for solar heat to a tubular heat transport system

ABSTRACT

A solar collector is made from a straight tubular metal heat pipe having an evaporator section and a condenser section and two elongate flat solar-heat metal absorber plates. A plurality of equally spaced parallel cuts is formed in each plate, with the cuts extending transversely of the longitudinal direction of each plate. The two plates are disposed one on the other with their respective parallel cuts in alignment; and alternate portions between consecutive cuts are deformed in opposite directions to provide alternate oppositely disposed semi-cylindrical portions. The evaporator section of the heat pipe is inserted into the resulting cylindrical space; and the semi-cylindrical portions are mechanically pressed against the evaporator section. The two plates are then bent away from each other into an outwardly extending X-shape.

This invention relates to a method of connecting at least oneplate-shaped absorber for solar heat to a tubular part of a heattransport system which contains a working medium for the transport ofheat.

U.S. Pat. No. 4,133,298 describes a solar collector which comprises asolar heat absorbing plate-shaped absorber which is thermallyconductively connected to the evaporator section of a heat pipe whichcontains a working medium which transfers the absorbed heat to thecondenser section of the pipe which can be made to exchange heat with afurther heat transport system. The plate-shaped absorber and theevaporator section of the heat pipe are enveloped by a glass envelope inwhich a subatmospheric pressure prevails. The absorber is connected tothe heat pipe by way of soldering.

The present invention has for its object to provide a method which issimpler and less expensive and which affords a suitably rigidcombination which is not subject to warping at elevated temperatures andwhich ensures suitable transfer of heat between the absorber plate andthe pipe.

The method in accordance with the invention is characterized in that anelongate absorber plate is provided with a number of parallel cuts whichare situated at regular distances from each other and which extendtransversely of the longitudinal direction of the plate, after which theplate portions situated between the cuts are pressed out of the plane ofthe plate so that the respective portions situated on either side of acut are pressed to different sides of the plate, after which the tubularpart is slid between the deflected plate portions.

A suitably thermally conductive connection can thus be realized betweenthe absorber plate and the tubular part by means of very simple means,the assembly being very rigid and free of warping, even at elevatedtemperatures, because the absorber plate symmetrically encloses the heatpipe.

If the pipe is not retained in a clamping manner after having been slidbetween the plate portions, the relevant plate portions are pressedagainst the tube in a clamping manner during a next procedural phase inaccordance with the invention.

In a further preferred embodiment, the deflected plate portions have aradius of curvature which exceeds that of the tubular part, therespective portions on either side of the pipe being pressed towards theplane of the plate during which they are at least locally plasticallydeformed. Thus, suitable clamping is achieved and also suitablecontacting of the tubular part by the plate portions.

In order to prevent the clamping effect between the plate portions andthe tubular part from being lost at elevated temperatures, in a furtherembodiment in accordance with the invention the material of the absorberplate is chosen so that the plate maintains its resilience at least atthe maximum temperature occurring during operation.

Instead of using one plate, the present method can also be performedwith a plurality of plates which are arranged one on the other. Afterthe connection to the tubular part, the plates can be deflected untilthey all extend more or less radially with respect to the pipe.

A further method of connecting two plates to a tubular part inaccordance with the invention is characterized in that each of the twoabsorber plates is provided along its longitudinal axis with similarcut-outs which are situated at mutually equal distances from each other,after which the plate portions remaining between the cut-outs are allpressed out of the plane of the relevant plate to the same side, afterwhich the two plates are fitted one into the other by way of theextruded portions and the tubular part is slid therebetween, after whichthese portions are firmly pressed again, if necessary, and the platesare bent one away from the other.

The invention will now be described in detail with reference to theaccompanying drawings, in which:

FIG. 1 shows an absorber plate with cuts.

FIGS. 2 and 3 are sectional views of a pressing device, FIG. 3 beingtaken along line III--III of FIG. 2.

FIGS. 4 and 5 are a sectional view and a perspective view, respectively,of an absorber plate having portions which have been extruded to bothsides.

FIG. 6 is a perspective view of a heat pipe.

FIG. 7 is a perspective view of a combination of a heat pipe and anabsorber plate.

FIG. 8 is a sectional view of a further pressing device.

FIGS. 9 and 11 are perspective sectional views of two other embodimentsof an absorber plate combined with a heat pipe, FIGS. 10 and 12 beingsectional views taken respectively along line X--X of FIG. 9 and alongline XII--XII of FIG. 11.

FIG. 1 diagrammatically shows a flat plate-shaped absorber 1 which ismade of metal, for example, aluminium and one side of which is providedwith a black layer, for example, a layer which selectively absorbs solarheat.

This plate is provided at regular distances with cuts 2 by means of apunching or cutting operation.

As shown in FIGS. 2 and 3, the plate 1 with the cuts 2 is inserted intoa pressing device 3 (not further elaborated). The pressing devicecomprises a lower die 4 and an upper die 5, which are each provided overtheir full width with alternating cavities 6 and projections 7, theshape of which corresponds to that of the cavities 6.

The projections 7 on the respective dies are arranged so that theystrike only every other plate portion 8, 9 between the cuts 2. Duringpressing, therefore, the plate portions 9, 8 are pressed alternatelyupwards and downwards out of the plane of the plate 1.

The result is shown in the sectional view in FIG. 4 and in theperspective view in FIG. 5.

The evaporator section 11 of a straight heat pipe 10 (see FIG. 6) isthen slid into the channel thus formed by the deflected plate portions 8and 9. The condenser section 12 remains free. The diameter of the heatpipe 10 is slightly smaller than the diameter of the channel enclosed bythe portions 8 and 9. This means that initially the heat pipe is ratherloosely arranged between the portions 8 and 9.

In order to obtain suitable clamping of the heat pipe, the assemblyformed by the plate 1 and the heat pipe 10 is subsequently introducedinto a pressing device which is shown in a sectional view in FIG. 8.This pressing device comprises two dies 14 and 15. The dies 14 and 15include a trough-shaped recess 16, 17, respectively, having arectangular cross-section and a width which is slightly larger than thediameter of the section 11 of the heat pipe 10 and a depth which isapproximately equal to half the diameter of the section 11. When thedies are closed, the sharp edges of the recesses 17 and 16 will pressthe portions 8 and 9, respectively, against the heat pipe 10, theportions 8 and 9 then being plastically deformed so that after theopening of the dies, the portions 8 and 9 are clamped against thesection 11 of the heat pipe. A very intimate thermal contact is thusrealized between the heat pipe 10 and the absorber plate 1 and a highrigidity of the assembly formed by the absorber plate 1 and the heatpipe 10 is obtained. This assembly is shown in perspective in FIG. 7.

In a practical embodiment, use was made of an iron absorber plate of alength of 920 mm, a width of 617 mm and a thickness of 0.5 mm. Thisplate was provided with cuts at equal distances of 20 mm. The radius ofcurvature of the projections 7 and the recesses 6 of the lower die, andhence of the deflected portions 8 and 9, amounted to 8.5 mm. Thediameter of the evaporator section 11 of the pipe 10 amounted to 8 mm.

The recesses 16 and 17 had a depth of 4 mm and a width of 9 mm.

FIGS. 9 and 10 show a further construction which can be realized in thesame manner (heat pipe removed). Use is made of two plates 20 and 21which are arranged one on the other and which are together provided, asdescribed previously for one plate, with portions 22 and 23 which aredeflected out of the plane of the plates and wherethrough the evaporatorsection 11 of a heat pipe is slid. After the execution of the describedmethod, the plates 20 and 21 are bent apart in X-shape, so that fourabsorber surfaces are obtained.

FIG. 11 (heat pipe removed) and FIG. 12 diagrammatically show anembodiment of a heat pipe 10 in combination with two absorber plates,the plates being provided along their longitudinal axes with cut-outs 24of equal dimensions which are staggered with respect to each other inthe plates. Subsequently, the portions 25, 26 situated between thecut-outs are bent out of the plane of the plates in the describedmanner, after which the deflected portions of the one plate are insertedthrough the cut-outs of the other plate. Subsequently, the heat pipe isintroduced; the pipe may already be clamped by the portions 25 and 26.If necessary, further clamping is realized by means of a press as shownin FIG. 8. After this operation, the plates are suitably thermallyconductively connected to the heat pipe. Subsequently, the plates arebent apart into the desired X-shape.

What is claimed is:
 1. A method of connecting a straight tubular metalheat pipe having an evaporator section and a condenser section to twoelongate flat solar-heat metal absorber plates, which comprises forminga plurality of equally spaced parallel cuts in each absorber plate, saidcuts extending transversely of the longitudinal direction of eachabsorber plate; disposing the two absorber plates one on the other withtheir respective parallel cuts in alignment; deforming alternateportions between consecutive cuts in opposite directions to providealternate oppositely disposed semi-cylindrical portions, the twoabsorber plates remaining in contact with each other; inserting theevaporator section of the tubular heat pipe in the cylindrical spaceformed by said alternate oppositely disposed semi-cylindrical portions;mechanically pressing said semi-cylindrical portions against theevaporator section of the heat pipe to clamp the absorber plates theretoand to provide thermal conductive contact therewith; and bending therespective remainders of the two absorber plates away from each otherinto an outwardly extending X-shape with respect to the heat pipe.
 2. Amethod of connecting a straight tubular metal heat pipe having anevaporator section and a condenser section to two elongate flatsolar-heat metal absorber plates, which comprises forming a plurality ofequally spaced cut-outs in the longitudinal direction of each absorberplate, the length of each cut-out being equal to the spacing betweenconsecutive cut-outs; deforming the portions between consecutivecut-outs of each absorber plate in the same direction to provide spacedsemi-cylindrical portions; arranging the two absorber plates in contactwith each other with their respective semi-cylindrical portionsalternately oppositely disposed; inserting the evaporator section of thetubular heat pipe into the cylindrical space formed by said alternateoppositely disposed semi-cylindrical portions; mechanically pressingsaid semi-cylindrical portions against the evaporator section of theheat pipe to clamp the absorber plates thereto and to provide thermalconductive contact therewith; and bending the respective remainders ofthe two absorber plates away from each other into an outwardly extendingX-shape with respect to the heat pipe.